1965 Pontiac GTO Flex plate

MOTOWN1965

MEMBER
1965 PONTIAC GTO
V8
2WD
AUTOMATIC
95,106 MILES

I have a 65 restored gto 400 ci 700r4 transmission. Last year the flex plate cracked and I had it replaced.650 miles later it appears to have gone bad again. Yesterday I was coming home and the gradual rattle started just like last year and by the time I got home the noise was as bad as the first time. What could cause it to go bad, loose bolts, another crack, the crank. Just asking for possibilities?Thanks,
roger

1 Reply

HMAC300

MECHANIC
48,601 POSTS

First a 65 has a 389 in it not a 400 unless it's been replaced. Then you are using a modern transmission for an older car which is ok, but the torque converter should be balanced for the motor that it's used on. This may be the problem as I don't remembmer if POntiacs are internally or externally balanced. Also the converter on a 700R4 has a longer nose on it and it may not be going into the crank causing a imbalance problem. The later model crankshafts are cut out for this torque converter. You could check at an engine rebuilder and he could tell you if it's externally or interally balanced. If it's external then you may look into the balance on teh troque converter. Also if it's broken flex plates you should check the oil pump bushing as it may be bad as well.